1. Field of the Invention
The present invention is related to a solar energy baking apparatus, especially to a solar energy baking device for automatically preventing an extreme baking temperature. This invention's function is for baking fruit, food, tea, or any commodity wherein the objective is to reduce the moisture content through the use of solar energy.
For the purpose of this application, we shall utilize as an example the baking of tea.
2. References on Related Prior Art
The objective in baking tea is to control the baking temperature within a proper range so as to reduce the moisture content of the tea leaves. In the process, proper control of the temperature will cause the tea to generate a special fragrance. In baking tea by solar energy, a key issue is preventing an extreme baking temperature. The means of controlling the temperature is also very important.
The conventional tea baking apparatus include either an electric heater baking apparatus or a coal energy baking apparatus. However, all of them use costly energy, waste natural resources, and contribute to pollution.
Accordingly, the present inventors have researched solar energy baking devices by using vacuum solar energy heat collectors during work at the Energy and Resource Laboratories, Industrial Technology Research Institute, Taiwan, and a previous invention has been awarded a patent, Taiwan Patent No. 111930, September, 1996.
The solar energy baking apparatus includes a solar energy heat collector, photoelectric elements, D. C. deceleration motor, and a driving device. The tea is located within the inner tubes of the baking containers. Through selective coating adhered to the outer surface of the inner tube, solar radiation thermal energy may be absorbed for baking tea.
In the baking apparatus, the deceleration motor driven by photoelectric elements will drive the baking containers to rotate so that the tea within the tube will be heated uniformly. Thus, the tea quality may be retained. The vacuum heat isolation layer effectively prevents heat loss, so that the whole baking process is more rapid and energy saving.
However, the temperature within the baking containers of Taiwan Patent No. 111930 will oscillate with the variation of solar radiation, therefore, the temperature during baking can not be controlled. Moreover, since the baking time can not be controlled, the quality of baking is unsteady.
According to the Taiwan Tea Experiment Station, if tea is baked for four to six hours in 100.degree. C., or two to four hours in 120.degree. C., the tea will generate a fragrant smell and the quality of low class tea will be improved. The preferred baking temperature of tea is 120.degree. C. If the baking temperature is over 150.degree. C., the tea is easily burned. Therefore, it is imperative to control both the temperature and time in the baking of tea leaves.